In the current state of the art, an objective lens and a folding mirror are used to focus a light beam onto an optical recording medium.
SPIE Vol. 237, 1980, International Lens Design Conference (OSA), pp. 439-445, shows the use of concave aberration corrected holographic gratings to diffract and focus.
U.S. Pat. No. 4,004,081 shows a parabolic mirror which simultaneously performs the functions of focusing device and deflection mirror.
U.S. Pat. No. 4,203,652 shows a beam of light from a semiconductor laser having different angles of divergence and different origins of divergence being collimated or efficiently treated into a circular spot light by a beam shaping optical system.